(a) Field of the Invention
The present invention relates to nickel powder having a specific particle size distribution or specific powder characteristic properties, such nickel powder in which a fatty acid is supported on the surface of the nickel particles, a method for preparing these powdery nickel products and a paste containing such a powdery nickel product and used in making an electrode for electronic parts. More specifically, the present invention pertains to nickel powder having a specific particle size distribution or is suitably used in a paste for making an internal electrode powder characteristic properties, which or an external electrode for electronic parts, in particular, suitably used for preparing a paste for forming an external electrode, such nickel powder, in which a fatty acid is supported on the surface of the nickel particles, a method for preparing these powdery nickel products and a paste containing such a nickel powder product and suitably used for preparing a paste for forming an internal electrode or an external electrode of electronic parts, in particular, suitably used for preparing a paste for forming an external electrode.
(b) Description of the Prior Art
Conventionally, an external electrode (thick film-like electrode) has in general been formed on a ceramic electronic part or element such as a multilayer ceramic capacitor element by applying, onto the part or element, a conductive paste containing powder of a noble metal such as platinum, palladium, silver, a silver-palladium alloy and then baking the applied paste. However, there have recently been developed techniques which make use of base metals such as copper and nickel in place of the foregoing noble metals and an alloy of a noble metal and a base metal such as those disclosed in Japanese Un-Examined Patent Publication No. Hei 6-236707, in order to save the production cost and a great progress has been made in such techniques.
A copper powder-containing paste has widely been used for forming an external electrode for ceramic electronic parts or elements. However, nickel powder has a melting point higher than that of copper powder and the temperature-depending characteristics during sintering of the nickel powder are quite different from those of the copper powder. Accordingly, good moldability upon the formation of an external electrode cannot necessarily be obtained even if using, in a nickel powder-containing paste, nickel powder having a particle size distribution and powder characteristics identical to those of the copper powder used in a copper paste.
An electrode for electronic parts or elements is in general formed by applying a nickel powder-containing paste onto positions on which an internal or external electrode for ceramic electronic parts or elements is formed and then baking the applied paste. However, various problems arise in the practical operations for forming such an electrode. For instance, pores are formed within the resulting electrode and the joining strength of the resulting electrode is insufficient.